Photocatalytic　water　splitting　has　become　a　very　popular　research　subject　in　recent　years.　Consequently,　it　is　important　to　report　appropriately　standardized　experimental　data,　so　that　each　researcher　can　properly　understand　the　results　generated　by　others.　However,　experimental　methods　and　measures　of　photocatalytic　performance　are　not　yet　sufficiently　systematic.　In　the　present　manuscript,　experimental　procedures　and　standardization　of　photocatalytic　performance　are　described　in　relation　to　the　basic　theory　of　photocatalytic　water　splitting.　Photocatalytic　water　splitting　has　become　a　popular　subject,　and　there　have　been　increasing　reports　on　this　subject.　One　challenge　in　such　a　situation　is　reporting　appropriately　standardized　experimental　data,　so　that　each　researcher　can　properly　understand　the　others＇　results.　This　paper　provides　basic　information　concerning　the　experimental　setup,　data　acquisition　and　processing　methods,　and　standardized　denotation　of　photocatalytic　performance.　image